Materials which strongly absorb low energy thermal neutrons are used in various applications, for example, for general radiological shielding, as shielding for neutron detectors, for shielding components of an instrument from neutrons, and to define the collimation of a neutron beam. Boron-containing compounds, gadolinium-containing compounds and cadmium-containing compounds are often used for thermal neutron shielding. However, many of these materials are disadvantageous in that energy which is generated in the materials from the thermal neutron absorption is released from the materials in the form of gamma rays. Thus, additional shielding may be required to reduce the gamma-ray radiation field.
Lithium-6 (.sup.6 Li) containing materials have also been used in thermal neutron absorbing applications. These materials are advantageous because the excess energy which is generated by the thermal neutron capture results, not in gamma radiation, but in charged particles which generally exhibit no radiological problems. Generally lithium-6 shielding material contains the lithium-6 in the form of either lithium metal or lithium carbonate. However, these materials require encapsulation of the lithium-6, thus restricting use of the material in many applications.
German reference No. DE 3,635,834 discloses radiation shielding glasses comprising cerium-doped alkali metal lead silicate materials. The compositions may contain .sup.6 Li for absorption of neutrons. German reference No. 1,301,449 discloses neutron-absorbing glass materials containing B.sub.2 O.sub.3, Al.sub.2 O.sub.3, CaO and Li.sub.2 O. This reference also discloses that the Li.sub.2 O may consist of an oxide enriched with .sup.6 Li.sub.2 O. The Reade U.S. Pat. No. 4,255,199 and the Tiede U.S. Pat. No. 2,736,714 disclose alumina silicate glass compositions further containing an alkali metal oxide such as Li.sub.2 O and PbO. The Speit et al U.S. Pat. No. 4,520,115 and the Omori U.S. Pat. No. 3,808,154 disclose alkali metal silicate glass compositions which may further contain additional oxide materials. The Lee et al U.S. Pat. No. 3,640,890 discloses glass laser compositions containing SiO.sub.2, Al.sub.2 O.sub.3 and Li.sub.2 O. Additional silica glass compositions also including Li.sub.2 O and/or Al.sub.2 O.sub.3 are disclosed in the Bishop et al U.S. Pat. No. 3,216,808, the Dalton et al U.S. Pat. No. 3,369,961 and Chemical Abstract No. 107:63418r. The Hall et al U.S. Pat. No. 3,751,387 discloses radiation-shielding cementitious materials which may contain .sup.6 Li for thermal neutron capture.
Owing to increasing requirements for radiation shielding devices of various shapes and sizes for use in many different applications, there is a continuing need for new and improved radiation shielding materials.